Process for producing linear unsaturated dimers of α-alkyl styrenes

Abstract

A process for producing a linear unsaturated dimer of alpha -alkyl styrenes by heating alpha -alkyl styrenes in the presence of a silica-alumina catalyst, said catalyst consisting of alumina and silica in a weight ratio of 83/17</=Al2O3/SiO2</=96/4 and being substantially free of alkali is disclosed.

What is claimed is: 
     
       1. A process for producing a linear unsaturated dimer of α-alkyl styrene which comprises heating at atmospheric pressure to 10 kg/cm 2  g an α-alkyl styrene in contact with a silica-alumina catalyst, said catalyst consisting essentially of alumina and silica in a weight ratio of alumina to silica of from 83/17 to 96/4 and said catalyst being substantially free of alkali. 
     
     
       2. The process according to claim 1, wherein said α-alkyl styrene is heated to a temperature of from about 50° to about 200° C. 
     
     
       3. The process according to claim 1, wherein the α-alkyl styrene is α-methyl styrene, α-ethyl styrene, m- or p-methyl-α-methyl styrene or m- or p-isopropyl-α-methyl styrene. 
     
     
       4. The process according to claim 1, wherein said process is a continuous or batch process. 
     
     
       5. The process according to claim 1, wherein said catalyst is in the form of a powder, tablet or globule. 
     
     
       6. The process according to claim 5, wherein said powder has a particle size of 0.01 to 3 mm, said globule has a drop size of 3 to 20 mm and said tablet has a diameter of 3 to 20 mm and a thickness of 1 to 20 mm. 
     
     
       7. The process according to claim 4, wherein said process is continuously performed over a fixed catalyst, said catalyst bed is maintained at a temperature of about 50° to 200° C. and said α-styrenes are fed to said bed at a space velocity of 0.05 to 5 hr -1 . 
     
     
       8. The process according to claim 4, wherein said process is a batch process, said catalyst is in the form of globule, tablet or powder and said process is carried out at about 50° to 200° C. under atmospheric pressure to 10 kg/cm 2 . 
     
     
       9. The process according to claim 1, wherein two or more α-alkyl styrenes are dimerized. 
     
     
       10. The process according to claim 1, wherein said alumina for silica ratio is 85/15 to 93/7 based on weight. 
     
     
       11. The process according to claim 1, wherein said process is continuous and said catalyst has a density of 0.5 kg/l to 1.5 kg/l. 
     
     
       12. The process according to claim 1, wherein said process is conducted in the presence of less than 2.0×10 -4  mol/g of alkali.